Integrated charring and ore reduction apparatus



April 27, 1965 O. MOKLEBUST INTEGRATED CHARRING AND ORE REDUCTIONAPPARATUS Filed June 27, 1963 INVENTOR. OLA v fa/(L Esc/.57. BY h4,

TUPNEKS.

MMF.

United States Patent O 3,180,631 INTEGRATED CHARRING ANDl ORE REDUCTEONAPPARATUS Olav Moklebust, Bayside, N Y., assigner to R-N Corporation,New York, NX., a corporation of Delaware Filed June 27, 1963, Ser. No.290,982 4 Claims. (Cl. 263-32) This invention pertains to the solidState reduction of oxidic ores, such as oxidic iron ores and the like,in the presence of hot combustible gases anda low volatile, solidcarbonaceous reductant, and provides novel methods and apparatustherefor wherein the physical heat values as well as the chemical heatvalues of the hot combustible gases and the hot char resulting from thecharring of a relatively high volatile carbonaceous material, such ascoal, by partial combustion thereof, are utilized in reduction Vof theore. l

v In processes as heretofore practiced using solid, carbonaceousreducing agents for low temperature, solid state i ore reduction, oreand carbonaceous matter are usually mixed -andrheated up to reactiontemperature.. As the reaction temperatures are generally higher than thetemperaturesrequred for volatilization of the low volatile constituentscontained in the reducing agent, these volatiles areusually lost to theprocess proper. Because the ore-carbon mixtures are heated up in countercurrent to the direction of gas flow, the volatile matteris distilledolf at atemperature where its combustion is not needed and where itsreducing power is not effective due to the low temperature. In theseprocesses, therefore,the volatile matter` can only be utilized outsidethe reactor, forvr instance, by combustion for external heatingpurposes. Thus, most of the solid reductant processes prefer tousecoke,coke breeze or low volatile anthracites rather than high volatilecoals. However, in visualizing large commercial installations, theavailablity of low cost coke or lfil Patented Apr. 27, 1%55 lCe of thecharring kiln. The reduction kiln is provided at its feed end with astack containing a blower and damper for regulating the draft. The hotcombustible gases evolved in the charring kiln pass directly through thecommon delivery end housing into the reduction kiln. This housing isalso provided with means for separately discharging the hot reduced oreproduct and the hot char delivered from the ore reduction and charringkilns, respectively. For` initial heating of the charring kiln, a burneris provided at its feed end.

Both kilns Iare preferably constructed and operated in accordance withthe principles set forth in my United States Patent 2,829,042, therotary kiln construction of which employs a series of` air inlet tubespenetrating the rotary kiln wall at intervals therealong and thereabout,these ltubes extending to the kiln axis on the interior and beingprovided with outlets therein for directing the air flowvaxially of thekiln, and being provided exteriorly of the kiln with air inlet valvesfor adjustably regulating the temperature and combustion conditionsthroughout the kiln to provide optimum conditions of furnaceperformance. f v

' In accordance with the novel process of my invention utilizing theaforesaid apparatus, the coal to be charred is `crushed to approximatelythe size of char required for ore reduction in the ore reduction kiln.The so-crushed coal is fed continuously and progressively into therotary charring kiln. Initial heating of the charring kiln is providedbythe burner mounted at the feed end for introduction and ignition of anair-fuel mixture. As the coal passes progressively through the charringkiln, it is heated up andcharred, the necessary heat for maintaining theoperation being thereafter supplied by combusting a portion of the coalor combustible gases evolved therefrom. The necessary air foraccomplishing this is drawn into the charring kiln through the air inlettubes thereof, by the coke breeze in sufiicient quantities presents laserious prob- 5 lem, whereas coal is widely available at a relativelylow cost. Y v Coalmaybe .employed as the immediately available source ofthe solid reductant, by charring the same, and

concurrently reducingthe ore inthe presence of the hot combustible gasesand optionally also the low volatile, hot char resulting from thecharring process; Alternatively, the hot char may be admixed with thewet recycle solid'reductant, separated from the reduced ore product incontinuous reduction processes, thereby to provide the necessaryphysical heat to vd ry the recycle reductant and supply a low volatilemake-up char to offset that lost in forced draft provided by the stackblower in the ore reduction kiln. The hot combustible gases generated inthe charring kiln flow directly into theiorereduction kiln through thecommon housing, in which as above stated,

, the delivery end of the charring kiln terminates. rlhus the physicalas well as the chemical heat values ofthe hot charV gases are utilizedin the ore reduction process. The hot char delivered from the charringkiln may be conveyed directly to the feed end of the ore reduction fkiln and fed therein along with the ore and recycle char,

the process. In this way the physical heat values-of the 1 1 same, andprovide the necessary low volatile make-up hot char gas and Vchar aswell'as the vchemical heat values .thereof areutilized in reducing theore.

In accordance with one aspect of my invention, I have devised anintegrated coal charring and ore reduction method and apparatus whichutilizes the same operating techniques for both, thereby simplifying theoverall operation and' eliminating the necessity for a special charringoperation crew. f

The novel `apparatus of my inveniton is of a composite duo-rotary kilnconstruction, comprising a relatively small rotary charring kiln and alarger rotary ore reduction kiln, the delivery ends of which terminatein a stationary housing, common to the twoand the feed ends of which are`separatelyhoused in stationary housings individual thereto. Thefeed endhousings are, respectively, provided With means for feeding crushed oreand the solid reductant together with a uxing agent such as limestone ordolomite, if required, into the'feed end of the ore reductionkiln andcrushed coal or an equivalent high volatile, solid carbonaceousreductant into the feed end and lime or other fluxingagentif employed,thereby to l preheatthe same and thus expeditethe ore reduction.'`

Alternatively, the hot char may be admixed with the wet recycle char,separated from the reduced ore product delivered from the 'ore reductionkiln,'thereby to dry the and separating sequences, for providing cleanrecycle char where a low grade or contaminated coal is employed forcharring.

T-he use in the process of my invention of such a rotary kiln forcharring in conjunction with such a rotary kiln for ore reduction, hasunique and commercially control-` ling'advantages for reasons abovestated, and also in that the two kilns are operated as a unit bya'single operating crew.. A further advantage is that no restrictions astov quality or particle size are imposed with respect to the coal orother high volatile reductant to be charred, as compared to suchalternatives as uidized bed or vibrating grate charring techniques. Thelatter are applicable only tothe charring of relatively high gradecoals, which must be pre-crushed and screened to relatively specificparticle sizes, i.e., about 1 to1.5 inches for a vibrating grate fur-Having thus described the invention in general terms, i

reference will now be had for a more detailed description, to theaccompanying drawing, which shows diagrammatically and schematically theessential construction and ow diagram operation of a preferredembodiment for practicing the invention.

Referring to the drawing, the rotary ore reduction and charring kilnsare shown generally at and 11, respectively. Theorey reduction kilncomprises au elongated tubular kiln 1?., suitably lined and providedwith a pairV of spaced Abearing rings 13, 14, encircling the same, forrotatably Supporting the kiln in axially inclined relation as shown, onrollers journaled to bearing supports, Vas at 15, 16. The kiln isrotated by a motor 17, to theshaft of which isv keyed a pinion 18,meshing with a ringjgear 19, mounted on te kiln and extendingthereabout.

Disposed at the opposite ends of the rotary kiln 12, are

stationary Ihousings 2d, 21, comprising, respectively, a

feed end' housing at-the feed end, and a delivery end housing. Both endsare equipped with duid-tight, Water cooled seals between the rotary kilnand housingsras at At the feed end is located an apertured barrier whichpermits the kiln to be operated with a high kiln load 25,

without back spillage and with a maximum exit gas open` i ing for thekiln gases. At the delivcryend, the kiln 12 terminates in a retainingdarn Z7 for the kiln load, insuring a relatively deep bed depth in thispart ofxthe kiln.

Also in the rotary kiln 12, are mounted at longitudinally and radiallyspaced intervals, a series of air inlet tubes, asx

at 28, which extend from the exterior to the axis thereof. The exterior'ends of these tubes are iitted with manually or otherwise individuallycontrollml, air inlet valves, as

at 29, while the inner ends are provided with openings.,

which are directed rco-directional with the flow of gases i Y 43,through which an air-gas mixture is supplied'an burned Within the kiln.Thereafter the necessaryV heat for charring the coal is supplied bycombusting part of the volatiles evolved :from the hot bed i7 vof coaland char Within the kiln. The necessary Yair stream for charring thecoal is drawn into the charring kiln through the air inlet tubes 42, bythe draft provided by the stack blower 33 of the ore reduction kiln, asa result of which the hot char gases generated in the charring kiln 38will iiovv directly into the ore reduction kiln 12, through chamber 21into which both of these tubes extend in open-ended manner as shown. Thehot char passes out of the charting kilni38 into the chamber 21, as at48, andis discharged thence through'` a hopper containing a rotary starvalve, as at 49. Y Y

The hot char from the charring-kiln may be utilized in any of the' waysabove described.k Thus, as illustrated purely by Way of alternativeVrouting inV the'drawing, but not by Way of limitation to: anyparticular apparatus ernployedfthe hot char may, for example, be`delivered by gravity feed from hopper 49 into achute Se and thenceintoa hopper 51, which may be rotated to vdischarge the n hot charthrough the slanted hopper outlet 52 thereof, into any of hoppers 53,S4, 55, depending onthe position to' which the outletSZ is rotated, asat'52, 52a,52b.

If the hotchar is thusdeliveredinto hopperSS, it is conveyed thence overa suitable conveying system indicated schematically at 56, directly into`the hopper 35, at

thefeedr'end of theor'e' reduction kiln 10, along with thel ore, recyclecoke, and lime if the latter is employed, thus to preheat the Vinputcharge to the furnace and thereby expedite .the ore reduction, andalso'y to replace the char consumed in the orc reduction.`

If, Von `the other hand, the coal used for charring Yis contaminated ordirty, it maybe discharged from hopper 51 into hopper 53, into which thereducedore product discharged from the reduction kiln, is also deliveredvia chute S7, and the Aadrnix'ture cooleddirec'tly by discharging thenceinto aV quenching tank 53, 'orV alternatively is cooled indirectlyb'y-fe'eding `through an externally` cooled drum, and conveyed thenceinto a conventional separating apparatus 59, including screening,ymagnetic separation in the kiln, as at 3b, for controlling thetemperature and combustion conditions throughout the kiln, asdescribediin my patent aforesaid. The feed end housing2t) is connectedto a stack .31, mounting therein `a damper 32, and a blower or fan 33,for controlling the draft in the kiln. Also at the feed end, surge bins(not shown) are provided for storage of ore, limestone, fresh coke andrecycle, coke, respectively, the dischargel from which are fed by a beltconveyor 34, into a hopper 35, and thence, Y

by a screw conveyor 36 into Vthe kiln 121..` At thev delivery end, thereduced ore product/36a, discharged from the kiln, is delivered into thehousing 2E, and is discharged thence through a gas-sealed outlet, Vsuchas suitably cooled rotary star valve, as ,at 37, for providing arelatively, gas-tight discharge outlet.

The construction of the charring kiln 11 is substantially like that ofthe ore reduction kiln 10, and hence requires little comment. The rotarykiln unit `33, is rotatably mounted, as at 39, 4(1), in the same manneras kiln 12, above described, and is similarly motor driven, as at 41.Air inlet tubes are provided, as at d2,`for the same pur-Y pose as tubes28.

The rotary kiln 38 extends between Va stationary feed end housing 43,and the common delivery end housing Q11, as shown, being providedthereat with water cooled seals between the kiln and housings, the sameas for kiln 12, as above described.

At the feed end, the charring kiln 11, is provided with a hopper 44,into which the crushed coal is delivered, and discharged thence througha screw or gravity conveyor 45, into the rotary kiln 38.' ,For initialheatingrof the kiln 11, a burner 46 *isV mounted in the feed end housingand tabling, for removing Vthe ash `and separating the iron.

values from the recycle cokeor char. The latter is conveyed'thence asy.indicated schematicallyat 6i), into a 'rotatable hopper 61, similaryto hopper 51,`fron1iwhence it is discharged into a hopper `62] by'appropriate rotation of hopper 51 as indicated, and conveyed thence, asindicatedl ate, into the recycle coke or'char bin at the feed end oftheorereduction kiln 1?.

As a final alternative, the char from kiln 11, if `itis of good quality,may be discharged y-lrorn hopper 52 into* hopper 54, and conveyedthence,as indicated at 64, into a mixer 65, into which the. recyclecoke fromthe separator 59 is also discharged bypositioning hopper 61, asindicated at 61a, to discharge into hopper 66, which in turn clis-`charges into the mixer-.65 as shown.

Inthemixer 65,- the physical heat ofthe hotchar dries and preheatsthetwet, recycleY coke or char, or preheats the same if introduced in aVdry state, froni whence the preheatedand. blended mixture is dischargedVonto a screen 67, ythe fines Vthrough which are conveyed, as

, indicated at `68, Yand thence as` indicatedat 63, to the recyclecokebin; While the oversize'material, held .on thev screen, is delivered asindicated at 69, into a grinder 7d, and returnedtothe screenV forre-sieving, as indicated at 71.` v i It will be seenfromthe"foregoingdescription that the invention provides a process andapparatusfor integrated ore reduction and charring which vis ofuniversal application to the charring of all Vgrades., of 'carbonaceousraw material, and also irrespective of the charring temperature andduration of the charring cycle required for charring the same to anydesired low state of volatility, to the end of full and completeutilization in the ore reduction process of the sensible heat values ofthe resulting hot char and the hot char gases evolved. The charringtemperature may of course be adjusted to and maintained at any valuerequired by controlling the partial combustion of the carbonaceous rawmaterial in accordance with the controlled air intake through the airtubes. The duration of the charring cycle may be adjusted by controllingthe feed rate of the carbonaceous raw material through theV charringkiln and also by the speed of kiln rotation. n j f In this connectionitis to be pointed out that all high volatile, carbonaceous reductantsgo through the following cycle on charring. As the material is heatedup, the light volatiles, such as hydrogen, methane, etc., are irstevolved. As the temperature is further increased beyond the evolution ofthese constituents, the material softens due to liquefaction of theheavier volatiles, such as the vtars. To evolve these, the softeningstage must be followed by a baking period of substantial duration, ifthe structure of the remaining solid carbonaceous char is not to bedestroyed, i.e., particle size, porosity, strength, etc.

In the process of this invention, in which the charring is effected byfeeding the reductant progressively through a rotary kiln, whilecombusting a portion thereof under controlled conditions by introductionof air through the inlet tubes penetrating the kiln wall at intervalstherealong, the material 'is gradually heated up as it travels along thekiln, thus initially to evolve the light volatiles as the temperaturefor evolving the same is reached, following which with furtherprogression of the material along the kiln, a higher temperature isobtained such as to liquefy the heavier volatiles, with resultingsoftening of the char, while following this the material is subl jectedto the required prolonged baking in the remainder of the furnace toevolve the heavier volatiles and thereby discharge at the delivery endof the kiln, a strong, porous char of desired particle size, which hasbeen freed of volatiles to any desired degree.

Many coals or other high volatile carbonaceous raw materials, requireprolonged heating at temperatures as high as about 1900-2200 F. foreffective charring to a low state of volatility, temperatures which areeasily obtainable in applicants process wherein any desired degree ofheating for charring can be obtained byregulating the fraction of thecoal or other carbonaceous raw material,

, which is burned for charring the remainder.

lpresent in the coal or other carbonaceous raw material,

passes olf in gaseous form in the charring kiln and is thus effectivelyeliminated from-the system, so that the 1 resulting char freed therefromdoes not contaminate the iron of the ore reduction process.

Also with the process hereof, the rate of char and char gas productionis adjustable to meet the full requirements therefor of the orereduction kiln, and without excess or deficiency, this beingaccomplished by adjusting the rate of combustion of the high volatilereductant in the charring kiln in accordance with the char and char gasrequirements of the ore reduction process. The ratio of char to char gasobtained may be adjusted to meet the requirements for each in the orereduction process by appropriate selection of the carbonaceous rawmaterial or by appropriate blending of such materials from differentsources, as for example by blending a high Volatile raw material withone of low volatility.

Another advantage of the construction operation of this invention is,referring to FIG. 1, that there is no sudden or precipitous change ingas pressure in passing from the charring kiln 11 into the ore reductionkiln 10, as would be the case for example if the charring were effectedin a vibrating grate or other conventional type of charring apparatus. Avibrating grate or equivalent charring unit must be operated at apositiveV gas pressure within the hood in whichthe char gases areevolved and collected in order to prevent the inspiration of airthereinto with resulting combustion of some of the char gases. Since theore-reduction kiln of this invention operates in general at a negativegas pressure that is sub-atmospheric, the use of a vibrating gratecharring kiln would necessitate piping .the hot char gases from thecharring unit into the. reduction kiln through a conduit of dimensionsappropriate to produce the required gas pressure differential .inpassing from one to the other. In contrast to this in theconstructionhereof, employingV rotary charring and ore reduction kilns, eachprovided with valve controlled, spaced air tubes for controlling gaspressure as well as combustion conditions, the charring kiln may opendirectly into the vore reduction kiln as shown, so `that the singleexhaust fan provided in theexhaust stack of thereduction kiln draws thecombustion gases as evolved in the charring kiln for combustion in thelatter to provide the necessary temperature and combustion conditionsfor optimum reduction of the ore. In this connection the air intakethrough the valve inlet tubes of the charring kiln are adjusted foroptimum charring conditions while the air intake through the air tubesof the reduction kiln are adjusted for optimum ore reduction conditions,so that optimum charring and ore reduction conditions are obtainedautomatically in this Way. Y

This application is a continuation-in-part of my copending applicationSerial No. 80,296, tiled January 3,

1961, now U.S. Patent NO. 3,133,812, granted May 12,

What is claimed is:

l. Rotary kiln apparatus comprising: a pair of tubular kilns, meansmounting eachlkiln for rotation about its axis, with an end of one kilndisposed adjacent an end of the other, a stationary housing common tosaid adjacent kiln ends, and spanning and encircling the same,stationary end housings individual to the opposite ends of said kilnsand enclosing said ends, respectively, a stack containing blower anddamper units surmounting one'said end housing, means individual to saidend housings for feeding loose aggregate materials into said kilns,respectively, means for discharging loose aggregate materials from theadjacent ends of said kilns into said common housing and separatelydischarging the same therefrom.

2. Rotary kiln apparatus comprising: a pair of tubular kilns, meansmounting each kiln for rotation about its axis, with an end of one kilndisposed adjacent an end of the other, a stationary housing common tosaid adjacent kiln ends, and spanning and encircling the same,stationary end housings individual to the opposite ends of said kilnsand enclosing said ends, respectively, a stack containing blower anddamper units surmounting one said end housing, means individual to saidend housings for feeding loose aggregate materials into said kilns,respectively, means for discharging loose aggregate materials from theadjacent ends of said kilns into said common housing and for separatelydischarging the same therefrom, gas inlet tubes penetrating each saidkiln at spaced points therealong, said tubes having valve controlmeanslindividual thereto, exterior to said kiln.

3. Integrated ore reduction and charring apparatus,

comprising: a pair of tubular kilns, consisting of a rela- Y tivelysmall charring kiln and a relatively large ore reduction kiln, meansmounting each kiln in axially inclined `relation for rotation about saidaxis, with the lower Aends of the kilns disposed adjacent to oneanother, a stationary housing common to said adjacent kiln ends andspanning and encircling the same in substantially gas-sealed relation,stationary end housings individual to the opposite ends of said kilnsand enclosing the same in substantially gas-sealed relation, meansindividual to said end housings for feeding loose aggregate materialstherethrough and into the upper ends of said kilns, respectively, a`stack including blower and,damperunitsxsurmounting the end y housing ofsaid ore reduction kiln, rneansfor discharging loose aggregate materialsfrom the lower ends of said kilns into said common housing, and forseparately discharging .the same therefrom, respectively.

4. Integrated ore reduction and charring apparatus, comprising: a pairof tubular kilns consisting of a relatively srnall charting kiln and arelatively largerore reduction kiln, means mounting each kiln in axiallyinclined relation for rotation about said axis, with the lower ends ofthe kilns disposed adjacent to one another, a stationary Y a stackincluding blower and damper unitssurmounting the end housing of said orereduc'tionhkiln, means for discharging loose aggregate materials frornthe lower ends of said kilns into said common housing and Vfordischarging the same therefrom, respectively, gas inlet tubespenetrating each, tubular Akiln at spaced intervals therealong, andvalve'rneans, individual to said tubes external to said kiln forregulating the Vgas oW therethrough.vr

References Cited by, the rExaminer UNITED VSTATES PATENTS Y 1,358,75911/20 VLarsen 263-32 1,786,999 12/30 Hornsey a 75-36 2,323,289 7/43''Anderson '-M 263--32 2,829,042 4/58 vMoklebust 75-36 2,877,108 3/59VSmith 75-36 DAvtD L. RECK, PrfmaryfExamiheff WNSTON A. DOUGLAS,Examiner.

1. ROTARY KILN APPARATUS COMPRISING: A PAIR OF TUBULAR KILNS, MEANSMOUNTING EACH KILN FOR ROTATION ABOUT ITS AXIS, WITH AN END OF ONE KILNDISPOSED ADJACENT AN END OF THE OTHER, A STATIONARY HOUSING COMMON TOSAID ADJACENT KILN ENDS, AND SPANNING AND ENCIRCLING THE SAME,STATIONARY END HOUSING INDIVIDUAL TO THE OPPOSITE ENDS OF SAID KILNS ANDENCLOSING SAID ENDS, RESPECTIVELY, A STACK CONTAINING BLOWER AND DAMPERUNITS SURMOUNTING ONE SAID END HOUSING, MEANS INDIVIDUAL TO SAID ENDHOUSING FOR FEEDING LOOSE AGGREGATE MATERIALS INTO SAID KILNS,RESPECTIVELY, MEANS FOR DISCHARGING LOOSE AGGREGATE MATERIALS FROM THEADJACENT ENDS OF SAID KILNS INTO SAID COMMON HOUSING AND SEPARATELYDISCHARGING THE SAME THEREFROM.